In Breton, troménie means ‘walk around a sacred place’. The troménie in Locronan takes place every six years (next issue in July 2019) and is a totally unique event. Every time, thousands of people, some dressed in traditional costume, take part in the 12 km procession.
http://www.brittanytourism.com/to-see-to-do/events/brittany-s-main-events/tromenie-de-locronan-8-july-2018